Electrochemical degradation of doxycycline hydrochloride on Bi/Ce co-doped Ti/PbO2 anodes: Efficiency and mechanism

Doxycycline hydrochloride (DOX), a widely used broad-spectrum antibiotic, was used in large quantities and its residues in the environment caused a series of environmental problems. In this study, small amounts of bismuth (Bi) and cerium (Ce) were co-doped in the titanium matrix lead dioxide anode (Ti/PbO2) using the electro-deposition method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used for the characterization of the electrodes. And the prepared PbO2 anode was found to be mainly composed of beta-PbO2, and Ti/PbO2/Bi-Ce 03 (co-doped with 0.5 mmol.L-1Bi and 0.5 mmol.L-1 Ce in PbO2 anodes) had the best catalytic effect and surface structure. Compared with Ti/PbO2, doping improved its corrosion potential (21.82%), accelerated lifetime (108.33%), and degradation efficiency (43.62%) while reducing the electrochemical impedance (17.91%). It was proved by a single-factor experiment that the degradation rate of DOX was 100% at 10 min with a current density of 10 mA.cm(-2), electrolyte concentration [Na2SO4]= 0.1 mol.L-1, and pH= 4, which was the best degradation condition for DOX. In addition, the degradation of DOX fitted the first-order kinetic equation. The DOX degradation on Ti/PbO2/Bi-Ce 03 electrode was mainly attributed to direct oxidation and SO4 center dot-. Four possible degradation pathways were postulated using the results of high-performance liquid chromatography-mass spectrometry (HPLC-MS). The paper provided a new way for preparing Ti/PbO2 electrodes with high catalytic activity and longer lifetime, and also an efficient way for degradation of antibiotic DOX.

Automated summary

In this study, small amounts of bismuth and cerium were co-doped in the titanium matrix lead dioxide anode using the electro-deposition method. The Ti/PbO2/Bi-Ce 03 electrode showed the best catalytic effect and surface structure. Doping improved the corrosion potential, accelerated lifetime, degradation efficiency, and reduced the electrochemical impedance of the electrode. The degradation of DOX on Ti/PbO2/Bi-Ce 03 electrode was mainly attributed to direct oxidation and SO4-.